range96

I agree, to do a proper CPC, you would want to change the bore/stroke ratio (even if you stay with the same displacement), the crank (obviously), the intake track (to accommodate TT) and fuel injection (to provide adequate fuel for the TT). The valve train would not necessarily have to change, but likely would as well. I think that is why that engine is called LT7 (instead of LT6 with TT).

range96

You're right! The C8 was designed from the beginning to accommodate more, a lot more power and hybrid eAWD. Magnesium, CF, titanium here we come. The sky is the limit. CF body? Sure, the GT3R will have it.

ZRacerLE

This for sure

Jeff V.

LT7 is going to be a twin turbo version of the LT6. The details from the leaked TT CAD way back before the launch match up exactly with the LT6 block and heads. It's the same engine but with turbos hanging off the sides, and a water to air intercooler setup on top. LT6 + boost = LT7.

MitchAlsup

It is the same block as the 458 and 488.
displacement from 4.5L (458) to 3.9L (488)
horse power sent from 570 to ¿720?

range96

The LT7 will use the LT6 block but you can't simplify by saying it's a twin turbo version of the LT6. At absolute minimum it will have lower compression ratios, but likely will have the differences I outlined earlier. I wouldn't call the LS9 a supercharged LS7 or a LT5 a supercharged LT1.

Jeff V.

Obviously. I was more addressing this continued nonsense that it'll be cross-plane.

GrandSport 2017

Rkreigh

fpc works very well with turbos as does the higher revs
when running really high cyl pressure, engines live a bit better in the 6-8k range
It sounds daft, but when you thing about it, the piston spends less time at TDC under high pressure and has more firing events
even with the old LS pushrod motors we boost a muv at 6-8k and run higher boost there to make power and the cars are much faster
with the DOHC, this becomes much easier as the valvetrain is better with the solid lifter cams
I don't think the 7 will be as much different and it doesn't seem to want a CPC anymore. Look at what the euro guys do with their TT engines
GM will follow suite as there are some financial and engineering advantages with "less change" What makes you guys so sure the bottom end won't take to the boost?

I see a stronger lower compression piston, and maybe some better rods. With the 6 already turning up 8500 that's the sweet spot for a nice high PSI TT, why change it?

Turbo engines are a bit easier on the bottom end and by varying the boost with decent traction control the car will be a hoot

Red Mist Rulz

The block also needs to be changed. Currently, each pair of cylinders is completely isolated from the other 3 pairs. That won't work with the firing order and piston sequencing in a CPC. A DOHC CPC will be an entire new engine, not just a few new parts in the LT6. All the leaked and rumored information is that the LT7 is an FPC based on the LT6, not a CPC.

range96

Your're right, a lot more than meets the eye to convert from FPC to CPC.
I assumed the LT7 would go with CPC, but your argument is convincing. Both engines were designed side by side, so now I tend to lean to the LT7 being FPC as well.
I still think there will be plenty of internal changes to accommodate and optimize the boosted engine.

GrandSport 2017

I agree, the LT7 will use a different block from the LT6.
There ARE several head variants going into production, I'm sure there are several block variants as well.

traind

I know the old leaked cad showed turbos but I wonder of GM are going to just put the 160hp/125 ftlb electric motor on the front of the Z06 and call it done. 830hp awd with the same great sound as the Z06. Yes, 300 lbs heavier but 830 hp puts it at 4.8lb/hp vs Z06 at about 5.5. Competitive with the Ferrari 296. Add a bit more juice and competitive with the SF90

range96

I would rather take 850 hp and not being 300 lbs heavier.

traind

Agreed. But it's interesting to note that none of the other manufactuers have gone that high with turbo V8s. Not saying GM couldn't of course. Mclaren's 765LT , while likely underrated, is 100 off and Ferrari does 770 with the SF90 before electric motors.

RedLS6

I don't believe this is a limitation, no?

But I agree on the configuration, I'm leaning towards a twin-turbo flat-plane LT7 for many reasons I've touched on earlier.

range96

They are 4L engines. LT7 will likely be 5.5L.

range96

It would work, but not efficiently.

RedLS6

Talking about the sealed bay block here - why not - both cpc and fpc use a common shared crankpin, sharing the successive even/odd rods. Both of these cylinders are 90 degrees apart in each configuration, and from the sealed vacuum scavenging side, at most they may have to re-clock the oil scavenger pump lobes assuming they're timing them with any sealed bay pressure pulses, to account for the pairs of crank throws which are twisted apart to form the fpc configuration. The pressure pulses in each of the 4 sealed bays would have the same harmonic characteristics in each sealed bay. Now, intake and exhaust flow will be very different in a cpc but that's more block-independent.

Differences in the fpc block could be more aligned with stronger clamping head seal - bolts and strength items / cylinders and coatings. I wouldn't expect it to be drastically different though.

Red Mist Rulz

No argument there at all. Lower compression pistons, higher rate fuel injectors and pumps, probably different cams, and more.